1. Field
The present invention relates to the production of superconducting wires and, in particular, to those in which the superconductor is niobium tin (Nb.sub.3 Sn) or vanadium gallium (V.sub.3 Ga).
2. Prior Art
A number of processes have been developed for the production of superconducting wires; however, many of these require processing steps such as annealing, tin plating and ingot drilling. These steps add cost and processing time and unfortunately often result in decreased reliability and consistency of the wire or limit the length of the wire. The capacity to produce large, continuous lengths of conductors is important in applications such as magnets for fusion reactors.
In one prior art process for example, holes are drilled in a bronze bar and niobium rods are inserted to form a composite bar. The composite is then drawn down to form a wire. The wire is heat treated to cause the tin within the bronze to react with the niobium to form niobium tin. The difficulty with this process is the bronze work hardens during the drawing process, requiring a series of annealing steps which significantly increase manufacturing costs.
In another prior art process, a composite is formed by inserting niobium rods in a pure copper matrix. This composite is drawn down to form a wire which is passed through a molten tin bath, or which is electroplated with tin. The wire containing the tin coating produced by the bath or electroplating is heat treated to produce niobium tin. This added processing step involving the tin bath or electroplating increases costs and reduces the reliability of the wire.